In this article, the results of research on WRI of LUA Juodkiškiai experiment field (1999 – 2003) are discussed. Fertilization and other factors influence over potassium fluctuation, its balance and leaching into drainage water during crop rotation are analysed. In order to evaluate the potassium balance and its quantity passed together with rainfall, seeds, fertilizers and take with the yield (secondary and primary production) was established in plant residues and drainage water. When fertilizing with liquid manure, potassium balance was negative while growing perennial grasses as much potassium was needed to mature their yield. The investigations established that potassium concentration in drainage water and its leaching was increased by precipitation during the research period, and it was reduced by the amount of this element taking out with yield. Soil geochemical environment had influence on the increase of potassium supply in soil. It was established that long-term fertilization with liquid manure had raised the potassium supply in soil. However, from an ecological point of view, potassium leaching did not cause any problems. In all treatments the potassium concentration in drainage water did not exceed permissible concentration.

Blueberry cultivation is becoming more and more popular in Latvia, and several commercial plantations have been established recently. Highbush blueberries (Vaccinium corymbosum L.) are perennial and can grow without replanting for 50 years; therefore a choice of soil and its preparation have a great role. This article summarizes results of research carried out in commercial blueberry plantation established in 2004 on loamy Haplic Cambisol. Soil properties, especially reaction and organic matter content, initially were not suitable for blueberry cultivation, therefore deep tillage and application of soil conditioner (acid sphagnum peat) were done before planting and similar peat mulch was applied every second year. Berry yield of 4 blueberry cultivars, soil properties and the nitrogen, phosphorous and potassium content in growing plant leaves were determined. The obtained results showed that sphagnum peat is an effective material for lowering of soil pH in plant root layer (0 – 40 cm). Data about plant nutrient content in topsoil and subsoil as well as in growing plant leaves will help to develop criteria for soil fertility assessment and diagnosis of plant nutrition.

The investigations were carried out in the Lithuanian Agricultural University Water Research Institute land plots in the Endocalcari Endohypogleyic Cambisols (CMg-n-w-can). The basis of the investigation is 3 variants field experiment. Each variant consists of 3 in 0.54 ha drainage. The traditional arable farming is applied in variant I. In the variant II the land is not being cultivated, but in spring the perennial ryegrass (‘Lolium perenne L’) is being seeded into the spring barley and kept till spring. In the variant III the land is not being cultivated after the harvest and left for the rest till spring. The variant II is distinguished by the minimal mineral nitrogen content. Applied to cultivated and uncultivated land, the min N reserves are increased 51 - 83 and 33 - 40 and 11 - 101 and (38 - 134%) (to 9.5 - 14.3 mg kgE-1 and 152 - 68 and 154 - 61 kg haE-1). The average investigation of N concentration in the drainage water shows, that the minimum concentration of this element was in the second variant. Applied to the traditional farming and uncultivated land, the N concentration is increased by (30 - 42% to 34 and 37 mg lE-1). By average data the min N, leaching by drainage water in the variant II was minimal and about 27 kg haE-1. Applied to the arable farming and uncultivated land, the min N leching is increased (30 - 55%) (to 35 - 42 kg haE-1).

The objective of this study was to evaluate the main plant nutrient: mineral nitrogen (NH4 + -N and NO3 -N) dynamic in soil under fertilizing for obtaining high grain yields of winter wheat (Triticum aestivum L.) and to determine relationships between nutrient uptake and winter wheat productivity. The field study was carried out at the Research and Study farm ‘Vecauce’ of the Latvia University of Agriculture for two years 2012/2013 and 2013/2014 with winter wheat variety ‘Kranich’. Different nitrogen application rates (0, 85, 153, 150, 175, 180 and 187 kg haE-1) and timing were used for winter wheat. The content of nitrates NO3 -N and ammonium nitrogen NH4 -N was determined in the soil layers 0-0.20 m, 0.20-0.40 m, 0.40-0.60 m. Nitrogen management strategy during the plant growth period based on soil Nmin evaluating can improve N use efficiency and reduce environmental contamination. The maximum of mineral nitrogen content in soil in the vegetation period was observed at the beginning of stem elongation with a tendency to decrease. A significant impact (p is less than 0.05) of nitrogen fertilizer application was noted on the mineral nitrogen content in soil layer 0-0.20 m deep in both trial years. The increasing doses of nitrogen fertilizer raised the amount of mineral N in the soil profile. The significant impact (p is less than 0.001) of nitrogen application and year conditions was observed on grain yield. Close positive correlation significant at 99% probability level was observed between the grain protein content and nitrogen concentration mostly in all soil layers, but it was not found between the grain yield and nitrogen content.

In the world, hydrological models are often used in the modelling of ecological components. In the context of the Paris Agreement and the European Green Deal, it is necessary to develop GHG emission modelling capabilities. The development and refinement of the conceptual model METQ is necessary not only for the quantitative analysis of flow, but in addition to its refinement, it is possible to conduct interdisciplinary research in the subfield of ecohydrology, which studies the interaction of water and ecosystems, and in environmental engineering, which addresses the issues of reducing diffuse pollution and reducing greenhouse gas emissions, technology implementation issues, where water content in the soil and groundwater fluctuations play one of the main roles, for example, in the processes of the formation of nitrous oxide emissions. This paper examines potential GHG emission calculation algorithms used to successfully model GHG emissions from soils, with a particular focus on agricultural soils, which contribute one of the largest amounts of GHG emissions in national emission reports for the agricultural sector. Available algorithms for nitrous oxide nitrification calculations are reviewed and possible algorithms that can be used for modelling emissions from soils and integrated into the conceptual hydrological model METQ are discussed. The developed conceptual solutions for modelling GHG emissions from soils will develop a modelling tool that will be used to estimate the volumes of GHG emissions and evaluate the effectiveness of various GHG emission reduction measures, as well as to perform a complex assessment of the soil GHG balance.

Natural processes and human activity play a crucial role in altering the nitrogen cycle and increasing nitrogen oxide (N2O) emissions. Nitrous oxide isotopes 15N and 18O are important parameters that can help to explain the sources of N2O gas, as well as their circulation under different soil physical properties. The main goal of the study is to analyse the possibilities of using dinitrogen isotopes 15N and 18O, measured in soil samples, for the identification of N2O sources. A total of 16 plots were sampled. Each soil sample was assigned a code. Wetting of the samples was carried out to create wet aerobic conditions and wet anaerobic conditions. N2O measurements were performed in laboratory conditions using the Picarro G5131-i device. The 15Nα and 15Nβ values obtained in the measurement data were used to calculate the δ15NSP and δ15Nbulk values. The obtained δ15NSP and δ15Nbul values were analysed using two methods – descriptive statistics and Kruskal-Wallis test. The test showed that there are statistically significant differences between δ15NSP values (p-value <0.0001), and δ15Nbulk there was no significant difference (p-value 0.885).

It is generally estimated that gas, which generates more than half of the greenhouse gas (GHG) emission from waste industries in landfills, is seen as a serious environmental problem worldwide. It is therefore essential to promote management methods to reduce GHG emissions from landfills as well as other sources. One way of achieving this is the usage of different types of biocover applied to them. The aim of this study is to clarify the impact of the biocover created on GHG emissions. An experiment was conducted in laboratory conditions that studied the effectiveness of biocover developed in the laboratory. Three experimental columns with a diameter of 160 mm and a height of 1500 mm were created. Active compost saturated with water at a thickness of 500 mm was used as a source of methane, a permeable layer of sand at a thickness of 300 mm was further formed and finally covered with biocover. Biocover represented 60% of fine-fraction waste, 20% of soil and 20% of compost. The experiment was launched on June 6, 2022, and the first measurements were made two weeks later. All measurements were performed with the CRDS gas measurement device Picarro G2508 (Picarro Inc., USA California). All data analysis was carried out using Descriptive statistics methods. The largest reduction in emissions is projected directly for methane emissions, as biocover technology is appropriate to reduce methane emissions. Other GHG emissions are also expected to be reduced. NH3 emission measurements were also carried out to investigate the impact of the biocover on it. This experiment shows that the biocover created is effective and can be composed of material that has already been served. The experiment is intended to continue to obtain long-term data on the development of biotransformation and to develop more promising approaches in the future to reduce GHG emissions from landfills.